Homogenization is an industrial process which has long been in use and which is intended, in a fat emulsion such as, for example, milk, to split the largest fat globules into smaller fat globules and by such means stabilise the fat emulsion. For, for example, milk, this implies that cream settling is prevented, and the greater part of all consumer milk today is homogenized.
The homogenization normally takes place by a mechanical processing, such that the fat emulsion, which is at a high input pressure, is forced to pass at high speed through a very tight gap where the fat globules of the emulsion are broken up as a result of the turbulence which occurs at high speeds and by cavitation bubbles which implode in the liquid. The process takes place during a very short period of time and what happens during this period of time is that the speed of the fat emulsion on passage increases while the pressure reduces, with the result that the liquid will boil.
A homogenizer consists essentially of a large piston pump which gives a high pressure, and a counterpressure device, where the homogenization proper takes place. The counterpressure device, the homogenizer valve in turn consists of a pressurised, resilient valve cone, a valve seat and a wear ring, and a valve housing which surrounds the valve cone and the valve seat. The valve cone and the seat are normally rotation-symmetric and are disposed such that, between these two parts, a radial throttle occurs, which constitutes a homogenization gap. The height, width and length of the gap determine the volume at which the homogenization takes place. This volume should be as slight as possible in order to obtain an efficient homogenization. The gap height is reduced at a higher pressure of the liquid which is to be homogenized, at the same time as a greater flow implies that the gap height is increased.
Above all in the homogenization of pasteurized milk, compared with UHT-treated milk, use is made of lower pressure at the same time as the intention is to increase the flow quantity. This implies in turn that the homogenizer valve would need to be made larger, so that the gap height is reduced in order to obtain a thorough homogenization at this lower pressure and increased flow. However, it has proved that an up-scaling of existing, well-functioning homogenizer valves does not always work as satisfactorily in practice. The larger the pressurised surface obtained, the greater will be the forces which occur and the homogenizer valve must be even larger. At the same time, the costs for such a homogenizer valve increase by several factors.
Another method of solving the problem is to connect in parallel a number of homogenization gaps and, by such means, obtain an extension of the gap length and thereby a reduction of the gap height. This type of homogenizer valve with parallel-connected homogenization gaps has, however, an as good as fixed gap height. It also suffers from the drawback of suffering from wear in an uneven and uncontrollable manner, which negatively affects the homogenization result.
Swedish Patent Application SE 9600792-7 displays yet a further solution to how the gap length may be extended, in that the homogenization gap has been given undulating pattern along the radial throttle.